What we've done so far:

Monday, October 3
Wednesday, October 5
Friday, October 7
Monday, October 10 - Thanksgiving
Wednesday, October 12
Friday, October 14
Monday, October 17
Wednesday, October 19
Friday, October 21
Monday, October 24 - Midterm Examination
Wednesday, October 26
Friday, October 28
Monday, October 31

  

Monday, October 3
We can now move on: the rest of the Periodic Table!  Many-electron atoms!
We mentioned the approximations we must make, and the concept of shielding and effective nuclear charge.   We will return to these important concepts over the next few lectures and also you will look at them in Seminar 2. (We will return to this idea for our discussion of periodic trends.)

Pauli Exclusion Principle PEP for short!
REMEMBER: each orbital holds 2 electrons, with 2 different sets of 4 quantum numbers


Also, I mentioned the changes in orbital energies for many-electron atoms.  Looking at radial probability diagrams, we see that the 2s electron is more penetrating than the 2p electron, and this has an effect on orbital energies.  For my diagram of the energy levels for H, Li, Na, click here.  (Some of the lines which signify orbitals are a little darker than others, it is just a fluke of my drawing program and doesn't signify anything.)


SKILL: We learned the shorthand for energy level diagrams: orbital diagram to show where the electrons are, and an 7.8 Electron Configuration to tally up the electrons.  More next class...


Wednesday, October 5
Homework for today was to determine the maximum number of electrons in each subshell - s, p, d.

The number of electrons in the subshells match the number of columns in the different sections of the periodic table!

Rules for drawing ground state electron configurations:
The first rule: fill in order of ENERGY
The second rule: obey the Pauli principle
The third rule: follow Hund's rule (for degenerate orbitals)
We also have shorthand for filled rows: noble gas in square brackets [ ].
We defined core and valence electrons
- and then wrote valence electron configurations for the second row of the periodic table.


Friday, October 7
The Aufbau principle (or 7.9 The Building-up Principle) tells us how the order to fill orbitals: especially important for elements after Ar.

It is also possible to use electron configurations and orbital diagrams to talk about excited states.  We always obey the PEP, but can ignore the building-up principle and Hund's rule for excited states.

We talked about the Magnetic Properties of atoms.
Definition: diamagnetic - not attracted to a magnetic field, or slightly repelled by it (all electrons paired)
       paramagnetic - attracted to a magnetic field (some electrons unpaired)

Exercises:76, 80, 86, 92, and then 108, 114, 120, 124.

Monday, October 10
No class - Thanksgiving

Wednesday, October 12
Some clicker questions to get you started.
Discussed the reading assignment for today:  Chapter 8 - pages 305 - to the top of 313, and pages 325-336.
Ionic configurations.

8.3  Periodic Variation in Physical Properties requires a good understanding of effective nuclear charge.  We talked about Chang's description and compared it to the approximation you will make in Seminar 2.

Friday, October 14
More clickers as review of paramagnetic/diamagnetic and electronic configurations (note: excited states!)  Click here for the document. 

Atomic Radius

Trends:Down the group - bigger (bigger shells)
Across the row - smaller (effective nuclear charge gets bigger, electrons held more tightly)

Ionic Radius
Remember: Ions in an ISOELECTRONIC series all have the same number of electrons!

SKILL: given a list of atoms/ions, you should be able to put them in order of increasing/decreasing size

Exercises: 8.38, 8.43


Monday, October 17
8.4 Ionisation Energy
What is it? energy required to remove an electron from a ground state atom in the gas phase to make an ion
How is it measured? blast electrons at an atom, they will knock out some electrons, control the energy of the electron beam
We can take out more than one electron: I2, I3, etc.
 
Trends: Down the group, less and less energy is needed
Across the row, more and more energy is needed
 
A final note – all of these atoms are stable, and we have to BLAST out the electron.  Oxygen is still stable, it just requires a little less energy than we might have expected!
 
Exercises:  52, 54, 55, 56.
 

Wednesday, October 19
8.5 Electron Affinity
What is it? The negative of the energy change for the process of adding an electron to a ground state atom in the gas phase
Important: a more favourable anion will have a more positive EA
What if the anion is unstable?  (Experimentally, the electron doesn't "want" to "stick" to the atom...) A negative EA
Exercises: 62, 77, 82, 96, 100.

On to Chapter 9: Chemical Bonding I: Basic Concepts
First, an Intro into the Types of Chemical Bonding... 2 main types: Ionic and Covalent


Friday, October 21
See notes on my main page - we filled them in during class...
More clickers as review of ionic and atomic size.  Click here for the document. 


Monday, October 24 - Midterm Examination

I was sick, but Dr. McConnachie did a review for you!

Wednesday, October 26

More clickers for Lewis Diagrams.  Click here for the document. 
Onto more difficult examples ...

The L.D. is a model, so it doesn't always work - 9.9 Exceptions to the Octet Rule.
Electron deficient compounds contain Be or an element from the B group.  The octet will not be complete.
Elements past the second row can have extra electrons (expanded octet)

Friday, October 28

One more exception - species with odd number of electrons - a radical!
More clickers for Lewis Diagrams.  Click here for the document. 
Everybody should practice lots of Lewis diagrams.

REALLY REALLY REALLY IMPORTANT SKILL

SKILL: draw a Lewis diagram and calculate formal charges

REMEMBER THIS IS REALLY REALLY IMPORTANT!

A ton of the stuff to follow requires this skill.  You need to practice and become proficient at drawing these diagrams quickly.

Don't get behind on learning this skill, or the material to come will be more difficult to learn.  What time you invest now will be well spent.  Otherwise, you'll be spending more time later on, when the term is even busier!

Most of this class looked at 9.8 The Concept of Resonance: if you have more than one valid Lewis diagram with atoms in the same positions
How do we decide which is the best contributor?  Use Formal Charge and Pauling's Rule.

We use double headed arrows between our contributors.  The molecule doesn't flip from one to the other to the other.  Instead, these arrows show that all three combined represent the structure:  electrons are delocalised in resonance contributors; also charges can be delocalised.

SKILL:  draw the BEST resonance contributor + any equivalent contributors - we call these "major resonance contributors".  In the process of drawing these, you will usually also find some "minor resonance contributors"

IMPORTANT: we move electrons around, but not atoms.  All resonance contributors must have exactly the same skeleton of atoms connected by single bonds.

Homework for class on Monday - TeO2 and O3 - Major Resonance Contributors.
Exercises: 44, 46, 47, 52, 54, 56, 63.
I gave some other homework... click here for the answers to the first set,
click here for the answers to the second set.

Monday, October 31

More about the resonance hybrid - predict the delocalised bond length & bond order, and any delocalised charges.
More clickers for resonance.  Click here for the document.
Then we went on to discuss bond dissociation energies and the energy of a reaction (9.10 Bond Energy

SKILL: use the average values to calculate whether a reaction is favourable

Exercise: 9.72